The aims of this protocol are to determine the clinical, biochemical, muscle strength, muscle function, pulmonary function, EMG, and molecular genetic status of acid maltase deficiency patients. Interventions such as low carbohydrate diet, moderate daily exercise, and daily oral ephedrine therapy will be assessed at designated intervals. The laboratory will be used for oligonucleotide synthesis, DNA sequencing, DNA isolation, RNA isolation, PCR, Northern and Southern analysis, ultracentrifugation, and recombinant DNA techniques.